My computer has had 512mb of ram since I bought it used 1 year ago. The previous owner built the computer and installed 2 Kingston HyperX sticks of ram. One is 2700/256 and the other is 3700/256. I decided to buy another stick of ram and I purchased a 3500/512. The motherboard has 3 slots. I installed my new stick into the third slot and the computer would not boot. I removed the new stick from the third slot and the computer would not boot. I removed the two old memory sticks and put the new stick into the first slot and the computer booted fine. I added the 2700/256 stick and the computer would not boot. I removed it and I then added the 3700/256 in the 2nd slot and the computer would not boot. Right now it is running off of the one new 3500/512 stick. How can I get all of these sticks to work together? Cliffs: I added a stick of ram but it only works by itself, not with the other two sticks that were previously installed. How can I get all three sticks working?